Parallella Community

attached zip = clock distribution layout (Diptrace 2.9.0.1 beta)

picture:
- 2 x 5V power supply module
- clock distribution + measurement microphone interface module (a bit bulky but already-made enclosure)

I had the impression that female vocals were a bit constrained with my setup and that was confirmed by a couple of friends. Then I found a report on internet about my Fostex H320 midrange horns which described a similar feeling and so that was enough motivation to try something else.

With leftover pieces of wood I quickly built a couple of supports and indeed it does sound better with the new RCF H100 horns.

picture:
- trebble = Onken 5000T
- midrange = YL 35000 with RCF H100 horn
- low midrange = YL 55000 with MB-90 horn

Preliminary tests with vinyl

I was pretty curious to make a rough comparison of a listening test between CD and vinyl. I went to a friend's place to digitize (24-bit @88200) one of his vinyl records and then compared on my system with the very same interpretation from a CD.

Although there is a lot of room for improvements during the digitizing phase and the impression is for this particular case only, I found the result to be somewhat similar with the differences between CD and high resolution audio: the stage opens up and is lighter with digitized vinyl. However static and others pops on vinyl are VERY annoying!

picture #1
"the scene of the crime"

picture #2
parallella with AD converter (http://www.beis.de/Elektronik/ADDA24QS/AD24QS.html) digitizing to the micro-SD card

picture #3
2 beauties in action

Parallella is mating with ole'timer 300B triode (Sophia Electric)

For initial prototyping, the DAC module is split in 2:
- the DAC (DSD1794) with op-amps connected directly to the FPGA while testing both I2S and I2C
- the SPDIF receiver (CS8416) and 8-bit microcontroller to test I2C/RS232/clock

Volume control
The DSD1794 features a user programmable (I2C) digital attenuator for volume control.

The volume is set with a remote control on one digital amp which broadcasts the value through RS232 to the other digital amps linked together. The 8-bit uController can then adjust the DAC attenuation based on the value it decodes from the RS232 port.

Many thanks again to Christophe, the friend who helped me to decipher the digital amps serial protocol. Among his numerous skills, his knowledge of the Tact digital amps is awesome.

Parallella DAC

Since the TI DSD1794 DAC supports both oversampling (OS) and non-oversampling (NOS) as per the DDDAC project , first I planned to do a listening compare between those 2 PCM modes.

But this recent article on the Xilinx blog, also kindly pointed out by Andreas, looks pretty interesting as well:


Still plenty of work to do but so far so good, the first results sound promising

picture #1
Unfortunately the DSD1794 digital attenuation feature is available with OS mode only so I need to add volume control which I plan to do in the analog domain and I bought a couple of different ICs (MAS6116 and CS3310) to try out
The SDM module has been designed by researchers from UK

picture #2
the feasibility prototype to test both DAC-PCM and DAC-DSD using the same DSD1794
mono only for now

Haha Miyako Harumi! Really nice to find an Enka fan here!

You probably like Naomi Chiaki as well

DAC preliminary tests

workflow sequence: (only 1 Parallella used in loopback)
- generate a 32-bit 1kHz sinewave @88200 (PS)
- DMA to PL-BRAM
- output to SPDIF 24-bit @88200 (PL)
- loopback cable to SPDIF input
- extract SPDIF audio data 24-bit @88200 (PL)
- 2 parallel paths:
a) PCM NOS right-justified 24-bit @88200 (PL)
b) DSD 20-bit @2822400 (PL)
- feed both DSD1794A PCM and DSD inputs
- select PCM/DSD mode via I2C (PS)
- passive I/V stage as per DDDAC project (active stage disconnected)
- analog output connected to PC soundcard Digigram VXpocket
- AD conversion 24-bit @44100 SNR>94dB

same sequence for logsweep, but the recorded file was converted to 16-bit @88200 with CoolEdit before running the convolution with the inverse logsweep

no care taken for clean power-supply. The DSD1794A 5V analog power input is connected directly to USB 5V which powers the Parallella as well

getting into shape

I know nothing about high end audio but this project is AWESOME!

Your musical taste is awesome too.